* {
    margin: 0;
    padding: 0;
}

li {
    width: 600px;
    height: 400px;
    list-style: none;
    position: absolute;
}

.container {
    position: relative;
    width: 600px;
    height: 400px;
    margin: 0 auto;
    margin-top: 400px;
    overflow: hidden;
    margin-bottom: 400px;
}

img {
    width: 100%;
    height: 100%;
    display: block;
}

.btn span {
    display: none;
    position: absolute;
    z-index: 2;
    font-size: 40px;
    width: 40px;
    height: 40px;
    font-weight: bolder;
    color: #fff;
    cursor: pointer;
    background-color: rgba(0, 0, 0, 0.3);
    line-height: 36px;
    text-align: center;
    top: 190px;
}

.btn span:hover {
    background-color: rgba(0, 0, 0.7);
}

.prev {
    left: 20px;
}

.next {
    right: 20px;
}

.container:hover span {
    display: block;
}

#buttons {
    position: absolute;
    z-index: 2;
    width: 100px;
    height: 10px;
    top: 380px;
    left: 250px;
}

#buttons span {
    border: 1px soild #fff;
    border-radius: 50%;
    width: 10px;
    height: 10px;
    background: #fff;
    float: left;
    margin-right: 10px;
}

#buttons span:nth-child(1) {
    background: orangered;
}

.on {
    background: orangered;
}